AMN - SOUTH AFRICA: Metallurgical test work on Groenfontein

Bushveld Minerals, a diversified mineral development company with a portfolio of vanadium, titanium, iron ore, tin and coal assets in Africa, has released results from pilot-scale metallurgical test work and plant design at its Groenfontein tin deposit in Limpopo Province, South Africa.

The test work was intended to assess tin recovery on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flow-sheet design parameters. The test work has delivered the following positive results:

-          Expected recovery using gravity concentration of more than 70%, for grind sizes of -1 mm

-          Achieved commercial concentrate grade of 74.59% SnO2 (cassiterite - equivalent to 58.75% Sn)

-          Plant design and flowsheet under way

-          Final costing under way to determine capital and operating expenditure requirements for mining and processing plant establishment, together with ancillary infrastructure

-          Results to be incorporated into an updated business model focusing on the smaller-scale, near surface high-grade tin targets near-term production.

Bushveld released a Scoping Study on the Groenfontein and Zaaiplaats deposits in September 2014, which envisaged a mining rate of 691,000 tonnes/year at a head grade of 0.12-0.23% SnO2 to produce 610-1130 tonnes/year of refined tin metal post smelting.

Pursuant to the 2014 study, the company decided to revise the development plan for the project to focus on mining the higher grade zone of the Groenfontein and Zaaiplaats deposits and processing it using a relatively simple gravity separation flowsheet to produce a saleable concentrate product. The scope revision was driven by the company's interest in executing a low capex near-term production operation. The aim is to take advantage of a relatively buoyant tin market and establish Greenhills as a standalone tin asset.

In order to assess tin recovery parameters on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flowsheet design parameters, a large (500kg) sample of surface ore from historical workings at the Groenfontein deposit was submitted for additional metallurgical test work at Peacocke & Simpson, minerals processing experts specialising in gravity recovery.

The results show that at a top size of 1mm, >70% Sn recoveries are achieved for enhanced gravity concentration, less than 15% Sn is lost to tailings during spiralling, and shaking tables achieve at least 85% recovery, giving over 50% cumulative recoveries and a final concentrate grade of 74.59% SnO2 (58.75% Sn).

Consequently, a flowsheet has been developed for gravity separation, with crushing and screening and rod-milling to -1 mm. Material is concentrated via spirals and shaking tables to maximise recovery and SnO2 concentrate grade. The plant design envisages a 164,160 tonnes/year operation producing up to 510 tonnes/year SnO2.

The next step is to complete flowsheet design and mine-planning studies to determine mine capex and opex parameters, which will be incorporated in a revised financial model.

Bushveld Minerals CEO Fortune Mojapelo said: "The encouraging metallurgical results achieved support our view that high-grade cassiterite concentrates can be produced from the Groenfontein deposit with relatively good recoveries.

“With recently updated plant capex and opex estimates at hand, we look forward to finalising infrastructure and mine cost estimates while continuing to focus attention on accelerating smaller-scale mine development and commissioning. The tin market has been particularly positive in a generally negative commodity environment with the tin price up 18% since the start of the year on supply constraints."

www.bushveldminerals.com

News courtesy of International Mining